The present invention relates to an on-site apparatus and method for preparing aqueous cleaning compositions, including an electrolytic cell for producing and dispensing chlorine and sodium hydroxide for use in various cleaning and/or sanitizing formulations at the point of use.
Multi-component aqueous cleaning compositions are widely used in large scale industrial operations. The chemical manufacturing industry has traditionally employed large scale processes to manufacture either concentrated or dilute aqueous cleaners which are then shipped to the customers"" use locations.
Shipment of dilute aqueous compositions involves the movement of large volumes of products which are predominantly water. Transporting large quantities of a product which is mostly water is not cost-effective.
It was recognized that significant savings in transportation expenses could be achieved if concentrated chemical compositions were shipped to the use location, and then diluted, rather than transporting the diluted use solutions.
However, transportation, handling, and storage of concentrated chemical compositions can be quite hazardous.
It has therefore become more popular for manufacturers of cleaning and sanitizing compositions to provide methods which enable their consumers to manufacture diluted aqueous cleaning and/or sanitizing compositions at the point at which they are used which is referred to in the industry as xe2x80x9cpoint-of-usexe2x80x9d generation of chemical cleaning and/or sanitizing compositions. These methods typically employ some apparatus which prepares a variety of cleaning compositions from chemical concentrate vessels and a water supply. These devices are often microprocessor controlled so the end use chemical recipe(s) can be programmed into the device by the supplier of the chemical concentrates. In this fashion, chemical compositions can be tailor made for specific customers and for specific end uses thereby filling a variety of needs in a simple and cost-effective manner. Examples of such dispensers include U.S. Pat. No. 3,797,744, U.S. Pat. No. 4,691,840, U.S. Pat. No. 4,941,596, U.S. Pat. No. 4,976,137, U.S. Pat. No. 5,014,211, U.S. Pat. No. 5,203,366 and so forth.
However, these methods still require transportation of chemical concentrates, which in some cases, can be hazardous.
For instance, chlorine is a commonly used disinfectant. Chlorine gas is manufactured almost exclusively in combination with sodium hydroxide by the electrochemical reduction of salt brine solutions using one of three methods including the membrane cell, the diaphragm cell, and the mercury cell methods. This electrochemical process for producing chlorine in large chlorine/caustic plants using complex cells which keep the products from the anode separate from the products of the cathode is a well known art (see Kirk-Othmer""s Encyclopedia of Chemical Technology, Third Edition, volume 1, pages 799-865 and volume 8, pages 662-695, which are incorporated by reference). The electrolytic reaction produces chlorine and sodium hydroxide as co-products, and produces hydrogen gas as a by-product. The production of chlorine is typically accomplished in large facilities located near an economical source of power with NaCl as principle source of chlorine.
The problem is, however, at ambient temperature and pressure, chlorine is a hazardous, toxic, heavy gas which does not disperse readily if released accidentally into the atmosphere. Therefore, once chlorine has been collected, it is cooled and compressed and placed in heavy steel cylinders for transportation to the site of use. The hazards of chlorine in gas form require rigid regulation for packaging, handling and transport. Furthermore, the danger of its escaping from the cylinders remains a possibility. In extreme situations the concern over the possible accidental release of chlorine has resulted in the prohibition of the transport of chlorine through the streets of some communities, thus preventing the use of chlorine for some of its essential uses.
The problems of storing and transporting chlorine have been minimized in some instances by venting the chlorine from the chlorine/caustic plant with the co-produced sodium hydroxide to make sodium hypochlorite which can then be transported to the site of use. The concentration of sodium hypochlorite generally is in the range of about 15% by weight. While sodium hypochlorite (NaOCl) retains several of the useful properties of chlorine (e.g., disinfection, sanitation, odor control), it also increases the cost of transport since it contains almost 85% water, is unstable, and decays with time. Salt and excess caustic from the preparation of sodium hypochlorite are contaminating by-products transferred to the system being treated.
The present invention relates to an apparatus and method for producing aqueous cleaning compositions at the point of use, including an electrolytic cell for producing chlorine and sodium hydroxide directly at the site where they are intended to be used. The chlorine and sodium hydroxide may be combined with various chemical compositions to produce cleaning and/or sanitizing compositions at the point of use.
More particularly, the present invention relates to an apparatus and method for generating cleaning compositions at the point of use including a dispensing system for mixing a plurality of chemical compositions according to a predetermined recipe by providing at least one of a concentrated chemical composition such as a buffer, a surfactant, a solvent or a water conditioning agent and combining the concentrated chemical composition with chlorine, sodium hydroxide, or mixture thereof. The process includes an on-site generator of chlorine and sodium hydroxide by electrolysis of a sodium chloride solution.
Even more particularly, the present invention includes an apparatus and method for the preparation of multi-component chemical cleaning compositions at the point of use comprising at least one electrolytic cell for generating at least one of chlorine, sodium hydroxide or mixture thereof, a plurality of concentrated chemical compositions in a plurality of vessels, each vessel storing one of said plurality of concentrated chemical compositions, a controller for selecting a predetermined amount of at least one of a plurality of concentrated chemical compositions, and a delivery system in communication with the controller. The delivery system delivers a predetermined amount of at least one of sodium hydroxide, chlorine, or mixture thereof and a predetermined amount of at least one of a plurality of chemical concentrates to a common vessel.
The dispensing system may include a computer system such that the entire process is automatic, or it may involve an on/off system in which an operator starts and stops the system by pushing a button.
The apparatus may be used to prepare dilute aqueous chemical compositions, as well as concentrates without added water. The hazards associated with the transport and storage of large quantities of liquefied chlorine under pressure, and the need for transporting concentrated sodium hydroxide, are thus eliminated.